In traditional audio playback systems, multi-channel surround sound audio requires multiple speakers driven with signals in separate audio channels to create a “surround sound” listening experience. For example, 5-channel audio requires at least five speakers for left, center, right, left surround, and right surround channels. However, typically only two speakers are employed in the personal playback environment such as personal computers, earphones, or headphones. In order to achieve the surround sound listening experience with fewer speakers, a virtualizer can be set at the audio playback end to create the perception of sound sources of different channels.
Throughout this disclosure, the term “virtualizer” (or “virtualizer system”) refers to a system coupled and configured to receive a set of N input audio signals (indicative of sound from a set of sound sources) and to generate a set of M output audio signals for reproduction by a set of M physical speakers (e.g., earphones, headphones, or loudspeakers) positioned at output locations different from locations of the sound sources, where each of N and M is a number greater than one. N can be equal to or different than M. A virtualizer generates (or attempts to generate) the output audio signals so that when reproduced, the listener perceives the reproduced signals as being emitted from the sound sources rather than the output locations of the physical speakers (the sound source locations and the output locations are relative to the listener).
One typical example of such a virtualizer is designed to virtualize a set of 5-channel input audio signals and drive two physical speakers to emit sound that a listener perceives as coming from the true 5-channel sources, and create virtual surround sound experience for the listener without the large number of speakers that are required in traditional audio playback systems. In general, if a virtualizer is configured at the playback end, it will fully work to perform virtualization on all input audio contents to produce a surround sound effect.